1. Field of the Invention
The present invention relates to a method of producing a diamond film (membrane) for lithography with X-ray, electron beam, or the like.
2. Description of the Related Art
Recently, a semiconductor device has been highly accurate, and been highly integrated. In order to cope with the tendency, the pattern to be formed thereon is required to be finer, and lithography with X-ray or electron beam has been noted as a technique for realizing the requirement.
In order to form the fine patterns, an exposure apparatus has been generally used in many cases. As material for a mask membrane attached to the exposure apparatus, diamond, boron nitride, silicon nitride, silicon carbide or the like are proposed. Among them, diamond is considered to be optimal as material of a mask membrane for lithography with X-ray or electron beam, since it is excellent in Young""s modulus, etching resistance, high energy ray radiation resistance, or the like.
As a method of producing a film, there have been known methods using DC arc discharge, DC glow discharge, combustion flame, high frequency, microwave, hot-filament, or the like. Among them, the microwave CVD method is excellent in reproducibility, and can provide film with high purity, and thus it has been generally used in many cases.
However, even though the diamond film is produced in accordance with the method for production, growth of the film is sometimes difficult, since a nucleus of diamond is hardly generated. In order to overcome such a problem, there is known a method of abrading a surface of a silicon substrate or conducting ultrasonic scratch, before film formation, to accelerate generation of the nuclei of diamond. However, there are problems that surface processing cannot be conducted in high evenness and uniformity nor in good reproducibility.
Furthermore, it is proposed to grow a film with accelerating generation of nuclei of diamond by applying a bias voltage to the substrate (S. Yugo, Appl, Phys. Letter, 58 (1991) 1036). However, in the method, sufficient density of nucleus generation cannot be obtained and sufficient thickness of the film cannot be obtained in some cases, and uniformity of the film is sometimes insufficient.
The film is required to have excellent characteristics such as smoothness, mechanical strength, visible light transmittance, chemical resistance, electron beam resistance, radiation resistance or the like. If a film is produced by forming a diamond film on the silicon substrate in accordance with the above-mentioned microwave CVD method, and then removing the silicon substrate by polishing, wet etching or the like, smoothness and membrane stress of the film are often degraded. Therefore, all of the above-mentioned characteristics cannot be satisfied even by the method.
In order to suppress harmful effect due to X-ray or electron beam absorption to the minimum, the membrane is required to be a free-standing film having a thickness of 0.1 to 5.0 xcexcm. In order to form the membrane, tensile stress of the film needs to be 0.1 to 5.0xc3x97109 dyn/cm2.
In order to obtain a film having such a tensile stress, it is known that a diamond film can be formed by a microwave CVD method, with high concentration of methane that is a raw material gas. Under the condition, sufficient tensile stress of the film can be surely achieved, but crystallinity of the film is apt to be lowered. If the film is formed with low concentration of methane in the raw material gas, good crystallinity can be achieved, but tensile stress of the film is lowered, and thus the film has compressive stress and cannot be freestanding film.
As described above, it is quite difficult to produce a film having both of sufficient crystallinity and desirable membrane stress property that are basic properties of a diamond film. The causes thereof include interference of a lot of film formation parameters, since plasma is used in film formation.
The present invention has been accomplished to solve the above-mentioned problems, and an object of the present invention is to provide a method of producing a diamond film for lithography wherein a diamond film having high crystallinity and desired membrane stress can be formed on a substrate, and the film can be easily produced without degrading smoothness, membrane stress or the like after film formation.
To solve the above-mentioned problems, the present invention relates to a method of producing a diamond film for lithography wherein a ground film is formed on a silicon substrate, a diamond film is formed on the ground film using a mixed gas of methane gas, hydrogen gas and oxygen gas as a raw material gas, and then the silicon substrate is removed by etching treatment, followed by removal of the ground film by etching treatment.
As described above, if a diamond film for lithography is formed by the method that a ground film is formed on a silicon substrate, a diamond film is formed on the ground film using a mixed gas of methane gas, hydrogen gas and oxygen gas as a raw material gas, and then the silicon substrate is removed by etching treatment, followed by removal of the ground film by etching treatment, a film can be produced without degrading smoothness, membrane stress or the like. Accordingly, a diamond film optimal as a mask membrane for lithography with X-ray or electron beam or the like can be produced.
In that case, the ground film can be made of one or more of material selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr) and tungsten (W). Among them, silicon oxide, silicon nitride and silicon carbide are excellent in film-forming property, mechanical strength, visible light transmittance, and are preferable. Formation of the ground film can be conducted in accordance with a known method such as a spattering method, a reduced pressure CVD method, or the like.
Furthermore, according to the present invention, there is provided a method of producing a diamond film for lithography comprising forming a diamond film using a mixed gas of methane gas, hydrogen gas and oxygen gas as a raw material gas on a ground substrate, removing the substrate by etching treatment.
As described above, a film can also be produced without degrading smoothness, membrane stress or the like by the method comprising forming a diamond film using a mixed gas of methane gas, hydrogen gas and oxygen gas as a raw material gas on a ground substrate, removing the substrate by etching treatment, so that a diamond film optimal as a mask membrane for lithography with X-ray or electron beam or the like can be produced.
In that case, the ground substrate can be made of one or more of material selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr) and tungsten (W). Among them, silicon oxide, silicon nitride and silicon carbide are preferable.
In that case, etching of the above-mentioned silicon substrate is conducted with an alkaline aqueous solution, and etching of the above-mentioned ground film or the ground substrate is conducted with an acidic aqueous solution, to form a diamond film for lithography.
As described above, if the above-mentioned silicon substrate is etched with an alkaline aqueous solution and the ground film or the ground substrate is etched with an acidic aqueous solution, the substrate or the ground film can be surely removed by etching treatment, and the diamond film is never eroded by the alkaline aqueous solution. Accordingly, the diamond film can be surely and easily produced without degrading smoothness, membrane stress or the like.
If one or more of material selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr) and tungsten (W) is used as the above-mentioned ground film and the ground substrate as described above, the ground film and the ground substrate can be easily removed by etching treatment without damaging the diamond film, so that smoothness, membrane stress or the like of the resulting diamond film is not degraded.
According to the present invention, a diamond film is formed using a raw material gas comprising 0.1 to 20% by volume of methane gas, 70 to 99.89% by volume of hydrogen gas, 0.01 to 10% by volume of oxygen gas.
As described above, if the raw material gas comprising 0.1 to 20% by volume of methane gas, 70 to 99.89% by volume of hydrogen gas, 0.01 to 10% by volume of oxygen gas is used, high crystallinity can be maintained, and a diamond film having high tensile stress can be formed, even under the subtle condition that methane gas is diluted with hydrogen gas.
In that case, a diamond film is preferably formed with a microwave CVD method or a hot filament CVD method, keeping the temperature of the surface of the substrate at 700xc2x0 C. to 1200xc2x0 C.
As described above, if a diamond film is formed with a microwave CVD method or a hot filament CVD method, keeping the temperature of the surface of the substrate at 700xc2x0 C. to 1200xc2x0 C., tensile stress of the film can be easily controlled, so that desired tensile stress can be surely achieved without degrading crystallinity, and thus a diamond film suitable for lithography with X-ray, electron beam or the like can be produced.
The present invention also relates to a method of producing a mask membrane for lithography wherein a ground film is formed on a silicon substrate, diamond particles fluidized with gas are brought into contact with the surface of the ground film, a diamond film is then grown on the ground film, and subsequently the silicon substrate is removed by etching treatment, followed by removal of the ground film by etching treatment.
As described above, if a mask membrane for lithography is produced by the method wherein a ground film is formed on the silicon substrate, diamond particles fluidized with gas are brought into contact with on the surface of the ground film, a diamond film is then grown on the ground film, and subsequently the silicon substrate is removed by etching treatment, followed by removal of the ground film by etching treatment, a film can be produced without degrading smoothness, membrane stress or the like. Accordingly, a diamond film optimal as a mask membrane for lithography with X-ray or an electron beam or the like can be produced.
In that case, the ground film can be made of one or more of material selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr) and tungsten (W). Among them, silicon oxide, silicon nitride and silicon carbide are excellent in diamond film-forming property, mechanical strength, visible light transmittance, and are preferable. Formation of the ground film can be conducted in accordance with a known method such as a spattering method, a reduced pressure CVD method, or the like.
The present invention also relates to a method of producing a mask membrane for lithography wherein diamond particles fluidized with gas are brought into contact with the surface of a ground substrate, a diamond film is then grown, and subsequently the substrate is removed by etching treatment.
As described above, the film can also be produced without degrading smoothness, membrane stress or the like by the method wherein diamond particles fluidized with gas are brought into contact with the surface of a ground substrate, a diamond film is then grown, and subsequently the substrate is removed by etching treatment. Accordingly, a diamond film optimal as a mask membrane for lithography with X-ray or electron beam or the like can be produced.
In that case, the ground substrate can be made of one or more of material selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr) and tungsten (W). Among them, silicon oxide, silicon nitride and silicon carbide are preferable.
In that case, it is preferable that etching of the above-mentioned silicon substrate is conducted with an alkaline aqueous solution, and etching of the above-mentioned ground film or the ground substrate is conducted with an acidic aqueous solution, to form a diamond film for lithography.
As described above, if the above-mentioned silicon substrate is etched with an alkaline aqueous solution and the ground film or the ground substrate is etched with an acidic aqueous solution, the film is never eroded by the alkaline aqueous solution. Accordingly, the film can be surely and easily produced without degrading smoothness, membrane stress or the like.
If one or more of material selected from the group consisting of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr) and tungsten (W) is used as the above-mentioned ground film and the ground substrate as described above, the ground film and the ground substrate can be easily removed by etching treatment without damaging the surface of the diamond film, so that smoothness, membrane stress or the like of the resulting diamond film is not degraded.
According to the present invention, a diamond film having high crystallinity and desired membrane stress can be formed on the substrate, and a diamond film for lithography with X-ray or electron beam can be produced without degrading smoothness or membrane stress or the like after film formation.